1. Field of the Invention
The present invention relates to a light source device having a configuration of cooling a light emitter and a projection video display device, such as a liquid crystal projector, having the light source device.
2. Background of the Invention
A projection video display device of this kind emits light from a light source and projects an image of a liquid crystal light valve onto a screen 67. The device may be used by mounting a body case 41 on a desk 68 or the like as shown in FIG. 16A or by hanging the body case 41 which is turned upside down from a ceiling 69 as shown in FIG. 16B. An image projected is corrected so as to be upside down by a circuit in the body case 41 and formed correctly.
FIG. 17 is a sectional side elevation showing a light source 1 of a conventional projection video display device, and FIGS. 18 and 19 are front views taken along line C-C of FIG. 17 (See Japanese Laid-Open Patent Application No. H9-304835). The light source 1 is constructed by surrounding a light emitter 1a by a reflector 2. Since the temperature of the light emitter 1a becomes high during emission of light, it is necessary to cool the light emitter 1a with air. Generally, heated air rises, so that an upper portion of the light emitter 1a becomes hotter than a lower portion. The position of the light source 1 changes between the state where the device is mounted on the desk and the state where the device is hung from the ceiling. Therefore, a mechanism for concentratedly cooling the upper portion of the light emitter 1a in both of the states is conventionally proposed.
As shown in FIG. 17, in a body case 41 of the projection video display device, a first air passage 45 as an upper air passage to the light source 1 and a second air passage 46 as a lower air passage are formed, and a first movable fin 9 and a second movable fin 90 are disposed so as to be swingable in a plane almost orthogonal to an optical axis L in correspondence with the first and second air passages 45 and 46, respectively. As shown in FIG. 18, the movable fins 9 and 90 each have a shutter plate 92 for closing the air passage 45 at an end of a coupling rod 91 and a weight 26, and a center portion in the longitudinal direction of the coupling rod 91 is supported by a pivot 93 in the body case 41. On the swing passage of each of the movable fins 9 and 90, first and second stoppers 94 and 95 are respectively disposed.
In a state where the body case 41 is placed on a desk, as shown in FIG. 18, the first movable fin 9 tilts due to the weight 26 until it comes into contact with the first stopper 94 around the pivot 93 as a center, and the shutter plate 92 is deviated from the first air passage 45. Air flows from the first air passage 45 into the light source 1 to cool down the upper portion of the light emitter 1a. On the other hand, the second movable fin 90 descends due to the weight 26 and enters a horizontal state in which the coupling rod 91 is in contact with the second stopper 95, and the shutter plate 92 closes the second air passage 46. Air from the first air passage 45 is exhausted from a through hole 42 opened in a side face of the body case 41.
In a state where the body case 41 is hung from a ceiling, the posture of the device is as shown in FIG. 19, that is, upside down of the posture shown in FIG. 18. The second movable fin 90 allows an inflow of air from the second air passage 46, and the first movable fin 9 checks an inflow of air from the first air passage 45, thereby cooling an upper portion of the light emitter 1a. 
In the device, however, it is necessary to dispose the movable fins 9 and 90 above and below the light emitter 1a, so that the size of the device as a whole is large.